Such a kind of driving tool includes a head valve which controls flow of compressed air into a cylinder. When a trigger of the driving tool is manipulated, the head valve slides so that the compressed air flows into the cylinder to operate a piston, and a fastener is driven.
When a nailing work is performed, an ambient temperature of the head valve is decreased by an adiabatic expansion of the compressed air which passes through the head valve. Particularly, when the nailing work is continuously performed under an environment of low temperature and high humidity, water contained in the compressed air may be frozen by fall of temperature due to the adiabatic expansion. When an ice grain generated in such a manner is attached to the head valve, the ice grain grows gradually to be deposited in the vicinity of an O ring of the surface of the head valve, or to be caught in the O-ring groove. When the ice grain is caught in the O-ring groove to suppress the deformation of the O ring, a slide resistance of the head valve is increased so that sliding cannot be performed smoothly. When the head valve cannot smoothly slide, it results in the power-down of the driving tool or the increase of an air consumption amount.
A technology relating thereto is disclosed, for example, in Japanese Unexamined Patent Application Publication (JP-A) No. 2006-55939 in which the description is given about a configuration in which a ring-shaped flange portion is formed to protrude from an outer circumferential surface apart from an upper end edge of the strike cylinder, the cylinder seal formed of a material having a large heat insulating property and an elasticity is mounted to cover the surfaces of the upper surface of the ring-shaped flange portion and the upper end portion of the strike cylinder from the upper surface of the ring-shaped flange portion to the upper end portion of the strike cylinder, and a piston stop damping the strike piston at an upper dead center position and having a large heat insulating property and an elasticity is disposed on an upper side of the strike cylinder.
With such a configuration, although freezing occurs in the water of the compressed air by the adiabatic expansion of the compressed air, freezing water is hardly attached to the rubber having a large heat insulating property and an excellent elasticity, and although attached, the freezing water is easy to peel off so as to be easily blown away by the compressed air. Therefore, it is preferably prevented that the supply passage and the discharge passage of the compressed air are frozen.
In the technology described in JP-A-2006-55939, however, since a direct countermeasure is not implemented against freezing of a valve such as the head valve, the attachment of the ice on the surface can be prevented, but it cannot be prevented that the ice grain enters the O-ring groove, and the slide resistance is increased.
In this regard, an object of the disclosure is to provide a driving tool which can prevent a foreign matter such as ice from entering a sealed portion (O-ring groove and the like) of the head valve.